Rice-fish farming, an age-old practice in China, can be traced back more than 1 700 years, although recently it has been largely ignored. Integrated rice-fish farming in China is generally characterized by four basic components: (1) extensive use of land; (2) low input; (3) low yield; and (4) household consumption of rice-fish farming.
After the founding of the People's Republic of China, the government organized farmers and encouraged them to develop integrated rice-fish farming systems. As a result, hectarage under rice-fish farming reached 700 000 ha in 1959, but sharply declined in the 1960s and 1970s due to wide use of pesticides, reformation of cropping systems and unfavourable national economic policy during the «cultural revolution» period (1966-1976). During this period, acreage of rice-fish farming dropped from 40 000 ha to 320 ha in Guangdong province and a similar drop from 230 000 ha to 5 300 ha was documented in Hunan province. However, during the recent «reformation» and «opening» period, the government is again encouraging the adoption of rice-fish farmers.
With farmer initiative and assistance from the government, the adoption of rice-fish farming is rapidly expanding. It has traveled from Guangdong province in the south to Hei-Long-Jiang province in the north and has reached historical proportions with more than 1 million ha in 1986. Sichuan, Hunan, Guizihou and Fujian are the top four provinces in China.
Rice-fish systems are principally found in the areas of the Yangtze River basin and other parts of southern China, although some rice-fish can be seen in northern provinces. The traditional rice-fish systems presented here are found in both irrigated and rainfed areas. The improved designs are principally found in irrigated conditions. Most rice-fish farmers in China are «cooperative farmers» with small landholdings of 1 500 mē or less. Normal fishpond size is usually 1 000 mē.
Major component technologies of rice-fish systems in China are presented here.
1. Appropriate construction of paddy field
Design A: trench-pit design
This is an improved design with a small, shallow pit (1-2 mē) in the center of the field. Crossing trenches are dug to connect the pit to all side trenches. Increased water storage capacity offers a better refuge for the fish. This design raises rice yield by 10 percent and 1-2 times as many fish can be raised as compared with the traditional design.
Design B: trench-pond design
This design is a further improvement with a larger, deeper pond at one end of the field. Crossing trenches are also dug to connect the pond to all sides. This design significantly increases the water storage capacity and provides a better environment for the fish. It raises and stabilizes the yield of both rice and fish.
Ridged-field rice-azolla-fish model
This design was originally developed for swampy areas with the objectives of improving soil properties and increasing rice yield. Later it was, stepwise, integrated with azolla and fish. Rice is planted on the ridge, azolla as a feed for fish as well as a biofertilizer, and green manure and fish are stocked in the trenches.
Production data of rice-fish-azolla system
1 Chinese mu = 0.67 ha
Azolla is a small aquatic fern (usually 1-5 cm large) which can grow on saturated or moist soils. It is capable of doubling its weight in 3-5 days. Azolla has symbiontic bacteria which fix atmospheric nitrogen and can fix 3-7 kg N/ha daily. It contains 4 percent nitrogen on a dry-weight basis and is an excellent source of nitrogen fertilizer.
2. Basal fertilizer application
Physical injury to fish caused by inorganic fertilizers used in rice production can be a constraint to rice-fish systems. Necessary measures should be taken to minimize fish injuries. One such measure is to increase the amount of basal fertilizer application during the land preparation stage to approximately 80 percent of the total nitrogen and 100 percent of the total phosphorous requirement.
Reduced rice plant population within the ridged-field paddy design caused by the construction of trenches and refuge ponds is one farmer constraint to the practice of rice-fish systems. Farmers can lose as much as 10 percent of their paddy when constructing trenches and refuge ponds for rice-fish systems. To minimize reduced plant population (and potentially decreasing crop yield), plant spacing can be intensified by lessening the recommended distances between hills while maintaining the row spacing (20-25 cm). Normal hill spacing of 15-20 cm between plants can be cut in half, thus doubling the plant population in the side-rows of the trench.
4. Fish stocking considerations in rice-fish systems
5. Top-dressing fertilizer application
Top-dressing fertilizer is applied at the panicle differentiation stage (about 28-30 days to heading). A shallow layer of standing water in paddy is necessary for fertilizer application, but can increase the possibilities of injuring the fish. However, two alternatives exist which can help minimize these limitations.
6. Pest management
Stocking fry in newly
Stocking fingerlings in
Similar to fertilizer application, damage to fish health can be incurred with the application of pesticides to the rice crop. However, using simple techniques such as slow field drainage, allowing the fish to return to the trench/pond, cautious application of the pesticide, an allowance for a brief waiting period and re-irrigation of the field after application can help ensure minimal losses due to pesticide poisoning.
In fields with trench/pond designs, the water should be drained into the trench or pond, thus driving the fish into the refuge area before the application of pesticides.
In traditional paddy field design, fish can be driven to one-half of the field and pesticide application can be done in the other half of the field. The same procedure can be repeated to the other half of the field on the following day.
Issues for further consideration
With increased intensification in rice farming in China, the importance of azolla is likely to have declined. Which variability exists for different systems, i.e. rainfed, irrigated, traditional and improved, and what is the potential for further expansion? The market patterns of produced fish should be known before embarking on such an activity. Information on applications of nursery or growout systems by different types of farmers and the relevance of the system within their overall farm would provide important pointers for further applications.
The example provided on pesticide application in a traditional paddy field design only applies to chemicals which are not toxic to fish.